Correction: Boeing’s Rotte said Defiant would fly later “than” this summer.

WASHINGTON — The Sikorsky-Boeing SB-1 Defiant coaxial helicopter demonstrator is now undergoing rigorous testing prior to its first flight expected later this year, according to Boeing and Sikorsky company officials.

Defiant is likely to fly later than the summer, Randy Rotte, Boeing’s director of global sales and marketing for cargo helicopters and Future Vertical Lift, told Defense News in a recent interview.

In February, Lt. Gen. Paul Ostrowksi, the military deputy to the Army acquisition chief, told senators during a hearing, that the Army hoped to have Boeing’s aircraft fly by “late this summer.”

“First flight is an important milestone in any developmental program,” Rotte said. Yet, “I would submit that we are really focused on providing information to the Army throughout the whole flight test program to inform them as they go forward, as they are doing their analysis of alternatives, as they are doing their technical readiness assessment, as they are preparing for their program of record.”

The Army is assessing two flight demonstrators as part of an effort to inform requirements for its Future Vertical Lift family of helicopters that are expected to reach an initial capability in the 2030s.

[Future Vertical Lift poised to get Army out of the acquisition dark ages]

The Army’s Joint Multi-Role (JMR) program allows for yearlong flight test programs for both the Bell V-280 Valor tiltrotor aircraft and Defiant. The V-280 took its first flight while Defiant is still working toward that milestone.

Defiant experienced some delays due to a rotor blade manufacturing issue.

While the Army is looking for ways to expedite bringing FVL aircraft into service, recently released fiscal 2019 budget documents reveal the schedule could be slipping, not accelerating.

Sikorsky and Boeing are taking a very specific and calculated approach to getting Defiant airborne, according to Rich Koucheravy, Sikorsky business development director for FVL.

Koucheravy was even hesitant to name a specific date for Defiant’s first flight “because we are not focused on a date, per se; what we are focused on is when we do fly Defiant, we will have been through all of those activities, and we have already begun to build some of our ‘do not exceed’ criteria for our components, and we will fully test out the system so that we have a good productive test flight program,” he said.

“We will fly when it’s right and safe. We are not going to rush to get up on some artificial date,” Koucheravy said.

A Sikorsky-Boeing team is designing the second demonstrator aircraft -- the SB-1 Defiant -- in the JMR program ahead of the Army's FVL program of record. Defiant is expected to fly later this year.

The team is taking a phased approach to its test program that is not just centered on the aircraft, he added.

There are several big pieces at play. First, the team has a software integration lab in Stratford, Connecticut, that is hooked up to a flight simulator. “In that lab are all the hardware, the flight-worthy software, hardware boxes and of course all the servos, all the actuators that operate the flight-control systems for this aircraft in a lab,” Koucheravy said. “So when those pilots are working on the flight control software and developing that while they are flying the simulator, they are actually putting time on those flight-control components.”

The team is building “a lot of reliability, a lot of hours on all those hardware, software components that will inform our test program,” he said.

Boeing and Sikorsky are also building a powertrain system test bed next to where the aircraft is currently coming together at Sikorsky’s developmental flight center in West Palm Beach, Florida.

The test bed is essentially an aircraft that replicates Defiant on an iron frame strapped to the ground. The team is installing engines, transmission, rotor blades — all of the elements of a flight-worthy powertrain — and plans to get 50 or more good hours on all the major systems before Defiant flies, according to Koucheravy.

The aircraft is mostly built, he added, and the team has already tested “basically all of the systems on board the aircraft that support flight, so our hydraulics, our electrics, our avionics, our fuel systems, everything has been completely tested.”

The blade-manufacturing issue that slowed down the process to build the aircraft is “mostly behind us,” Koucheravy noted.

Part of the Joint Multi-Role program tasking includes coming up with ways to manufacture elements of possible future helicopters and requires the development and maturation of some advanced processes.

“Part of this is the reality of building a one-off, building prototypes using existing tooling, not purpose-built tooling, and these blades are definitely different than blades on Chinook, Black Hawk or Apache, whatever. And building them in a different manner, they have different properties to support,” Boeing’s Rotte said.

Boeing and Sikorsky had to push the envelope on the manufacturing side to build a rotor blade that had never been built before.

While the blades are now being steadily produced, “once you produce them, you have to test them, and we’ve got to go through all the elements after that. So it’s not just building them — it’s making sure your build process went according to plan” and that they fit on the aircraft, Rotte said.

“We are confident that as we finish the final build, we will be in the air in 2018 and we believe our plans support that and we are going to have a very successful, risk-reduced, deliberate and safe test program on Defiant because we have already learned a tremendous amount by iterating flight control software, hardware and all the power train before we lift off the ground for the first time,” Koucheravy said.

Jen Judson is an award-winning journalist covering land warfare for Defense News. She has also worked for Politico and Inside Defense. She holds a Master of Science degree in journalism from Boston University and a Bachelor of Arts degree from Kenyon College.

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